LONDON – Bitcoin, the world’s largest cryptocurrency, skidded almost 10 percent on Thursday to its lowest since late November, as a Facebook ban on cryptocurrency adverts and a growing regulatory backlash against the nascent market frightened investors.

Thursday’s drop to as low as $9,165.40 on the Luxembourg-based Bitstamp exchange BTC=BTSP left bitcoin trading at less than half the peak of almost $20,000 it reached in December. It slid more than 26 percent last month, in its worst monthly performance since January 2015.

Other cryptocurrencies, including Ripple, the third-largest by market value, and Bitcoin Cash, have also fallen by at least 10 percent in the last 24 hours of trading, according to Coinmarketcap.com. Ethereum was up slightly on the day.

Last year’s explosive rise in the value of digital coins and the flood of new retail investors drawn to the market have rattled global regulators nervous about a sector used largely for speculation.

Facebook (FB.O) said in a post on its website this week that it was banning all advertising that “promote financial products and services that are frequently associated with misleading or deceptive promotional practices, such as binary options, initial coin offerings and cryptocurrency”.

It was not clear whether the ban would affect all cryptocurrency adverts on the social media site. Facebook could not immediately be reached for comment.

India’s finance minister vowed on Thursday to eliminate the use of cryptocurrencies.

A $530 million hack of Japanese cryptocurrency exchange Coincheck late last week has also weighed on the market, along with a subpoena U.S. regulators sent to two of the world’s biggest cryptocurrency players, Bitfinex and Tether.

“Sentiment towards cryptocurrencies is turning sour with negative headlines pouring out from left, right and center,” said Fawad Razaqzada, an analyst at FOREX.com

“Concerns that Facebook is banning ads and major crypto exchanges shutting down have really silenced the hype and some people are probably having second thoughts about investing their hard-earned cash into digital currencies.”